Abstract 1. In a series of 57 cases of autoimmune hemolytic anemia it was found that 25 or 44 per cent had a relative reticulocytopenia at times of hemolytic crisis. The mortality rate in this group was significantly higher than in those who showed a reticulocyte response consistent with the severity of anemia. Special significance is given to the high mortality rate among the patients with idiopathic AHA. 2. Four illustrative cases are presented. 3. There is a discussion of mechanisms that may be responsible for reticulocytopenia in the presence of severe anemia and erythroid hyperplasia of the marrow.